Field of the Invention
The present invention relates to a laminate film, a backlight unit, a liquid crystal display device, and a method for producing a laminate film.
Description of the Related Art
Applications of a flat panel display such as a liquid crystal display device (LCD: liquid crystal display) (hereinafter, also referred to as “LCD”) as a low power consumption and space-saving image display device are widespread year by year. The liquid crystal display device is configured from at least a backlight and a liquid crystal cell, and usually further includes members such as a polarization plate facing the backlight and a polarization plate facing a viewer.
In the flat panel display market, enhancement in color reproducibility progresses as an improvement in LCD performance. With respect to this point, a quantum dot (also referred to as Quantum Dot, QD particle or quantum point.) has attracted attentions as a luminescence material in recent year. For example, when excitation light is incident from a backlight to a light conversion member including the quantum dot, the quantum dot is excited to emit fluorescent light. Quantum dots each having a different luminescence property can be here used to thereby emit light having a narrow half-value width, of red light, green light and blue light, realizing white light. Since fluorescent light by the quantum dots has a narrow half-value width, wavelengths can be properly selected to thereby allow the resulting white light to be designed so that the white light is high in luminance and excellent in color reproducibility. Such a technique of providing a three-wavelength light source using the quantum dots advances to thereby expand the color reproduction region from 72%, a current ratio according to TV (television) standard (FHD, NTSC (National Television System Committee)), to 100%.
The QD particle, however, is caused to have a reduced quantum yield due to oxygen and/or steam, and therefore is required to be used with being protected by a barrier film.
Japanese Publication of International Patent Application No. 2013-544018 has proposed a laminate film obtained by sandwiching a quantum dot-containing layer between gas barrier films high in oxygen barrier property on its opposite sides and steam barrier property for the purpose of protection of quantum dots from oxygen and the like, for stacking them.
The method of sandwiching the quantum dot-containing layer between the gas barrier films includes coating the quantum dot-containing layer with one of the gas barrier films and curing the resultant to prepare a film, and attaching the film to the other of the gas barrier films with a pressure-sensitive adhesive or the like interposed.